Pressure mechanism



Oct. 6, 1931. v -T. H. SEELY 1,825,704

PRESSURE MECHANISM Filed Dec. 2, 1926 2 Sheets-Sheet l J -g a Flgl.

' i 4 w A 0a. 6, 1931. T, H; SEELY 1,825,704

PRESSURE MECHANI SM Filed Dec. 1926 2 Sheets-Sheet 2 Fig. 6.

//Z //Z /0Z Patented Oct. 6, 1931 UNITED STATES.

TENT FFIE THOMAS H. SEELY, OF MELROSE MASSACHUSETTS, ASSIGNOR TO UNITED SHOE MA- CHINERY CORPORATION, OF EATER-SON, NEW JERSEY, A CORPORATION OF NEW JERSEY PRESSURE MECHANISM Application filed December 2, 1926. Serial No. 152,282.

This invention relates to pressing or clampngdevlces and is herein disclosed as embodled in a machine for compressing the heel seats of shoes.

Such machines comprise a die having the form deslred on the heel seat of the shoe,,a ack on which the shoe is mounted, and a pressure mechanism for forcing the-shoe and die together with a pressure amounting to sev- 1 erai tons. The combined thickness of the last and shoe varies between wide limits, in work broughtto such a machine, The pressure is conveniently applied by a toggle mechanism actin a ainst a stiff s rin and in order b b b,

pressure mechanism, to change its effective length as the jack and die are brought together on the work. It has been found, however v that under the unavoidable conditions of machine operation, such a Wedge will not 3 hold under. pressure by friction alone unless its angle be as small as 7*", and this generally limits its availability to a small range of work thickness, since theroomoccupied by a long wedge, andthe difficulty of manipulating it, are often prohibitive. i

The principal object of my invention is to provide a relatively short wedge which will hold by friction alone, under pressure, even though the angle between its relatively inclined surfaces is much greater than 7. To this end, I have provided a wedge having a beveled operating edge. .or face and have correspondingly formed the member cont-acting with that face. This increases the force pressing the beveled surfaces of the wedge and contacting member together, as Wi lb se n, and consequentlyincreases the friction b cen them. thus preventing the driving out of the wedge by pressure, of the wedged Sll'lffiCGSWlllh which it contacts.

Accordingly, an important feature of my invention comprises a pressure sustaining dev ce compr sing pressure sustaining members arranged for relative translational movement and a Wedge located between them for transmitting pressure from one to the other and for altering their distance apart, having one or both of its operating surfaces beveled, and the corresponding pressure sustaining memher or members having a wedge engaging surface complementarily shaped to increase the friction between the wedge and the pressure sustaining member.

Another feature consists in the wedge itself having one or both of its wedging surfaces beveled.

These and other features of the invention comprisingcertain combinations and arrangements of parts will be apparent fromthe following description of a preferred embodiment of the invention shown in the drawings, in which Fig. 1 is a broken away side elevation of the principal parts of the machine, showing the Work support raised into position ready for the application of pressure to a Work piece, which in the present instance is a shoe mounted on a last;

Fig. 2 is a section on the line II.I I of Fig.1;

Fig. 3 is a perspective view of the Wedge mechanism; 7

Fig. 4 is a side'view of the wedge;

Fig. 5 isa cross section on the line V V f F 4a i a Fig. Gis a cross section on the line YL-VI of Fig. 4;

Figs, 7 and 8 are diagrams illustrating the action of the mechanical forces involved.

7 The illustrated machine which is for forming the heel seats of shoes by pressure, is provided with a frame 10, as shown only fragmentarily in Fig. 1, in the middle part .of which is vertically slidably mounted a shaft 12 on the upper end of which is a work contacting member 14, shown in the present instance as a. jack for carrying a shoe last. Mounted on the frame above the shaft 12 and jack 14; is another work contacting memher 15, in the present instance shown as adie a machine.

or mold having the form to which it is desired to shape the heel seat of a shoe upon the last by pressure, such pressure being applied by vertical action of the shaft 12, as will be explained. The frame element on which the member 16 mounted may be rc garded as a fixed pressure abutment. Connected to the lower end of the shaft 12 is a toggle mechanism comprising two links 18 and 20 pivoted to each other and to an cecentric rod 22 at 2%. The upper toggle link 18 is pivoted at 26 to the end of the shaft 12. The lower toggle link 20 is pivoted at its lower end to a pin 28 (see Figs. 2 and 3) having flattened ends 30 arranged for sliding movement in a pair of slots 32 formed in a pair of upwardly extending walls 34 at the top of a plunger 36 which is mounted for vertical sliding movement in a sleeve 38 carried by the frame 10. Housed in the sleeve 38 beneath the plunger 36 is a heavy spring 40 arranged to receive the downward thrust of the toggle 18, 20 when the toggle is straightened to apply pressure to a work piece. Preferably, the spring 40 will be always held under some compression by any convenient mechanism such as a slot-and-pin connection 42 between the plunger 36 and the sleeve 38, the slot being long enough to permit the downward movement of the plunger 36 to the full extent required by the straightening of the toggle links 18, 20, and the pin contacting with the upper end of the slot when there is no work in the machine. The compression exerted by the spring 40 can be regulated by the vertical adjustment in the sleeve of a plate 44 upon which the lower end of the spring 40 rests. Such adjustment may be accomplished by any convenient mechanism, such as a screw, indicated in dotted lines, threaded into the bottom of the sleeve and operated through suitable gearing by turning the shaft 46.

The plate 44 may be regarded as the other fixed pressure abutment between which the pressure mechanism acts. The frame 10 is provided with suitable bearings for a shaft 48 driven from any suitable source of power and with a clutch of any suitable type arranged to cause the shaft to come to rest after each half revolution thereof. The link 22 has at its right-h and end in Fig. 1 an eccentric strap surrounding an eccentric 50 mounted on the shaft 48. The parts are so arranged that tripping the clutch will cause the shaft to revolve one-half revolution to straighten the toggle links 18, 20 and. that again tripping it will cause the links to take the position shown in Fig. 1 in which the work is released from pressure. The clutch may be operated by a conveniently disposed treadle 52 pivoted at 54 on the frame of the The treadle 52 is connected to the clutch by means of a rod 56.

Pivoted at 58 on the machine frame is a lever 60 through a hole in the rear end of which passes the rod 56, a spring 62 surrounding the rod and abutting against a collar thereon at its upper end and against the lever 60 at its lower end. The forward end of the lever 60 is connected by a link 64 to the joint at 26 at the lower end of the shaft 12. Depression of the treadle therefore rotates the lever 60 clockwise in Fig. 1 and raises the shaft 12. A lost motion connection 66 is provided between the treadle and the clutch operating mechanism so that the shaft 12 may be raised to its uppermost operative position before the actuation of the clutch, the spring 62 being heavy enough to carry the weight of the shaft 12 and the parts carried by it and being compressed somewhat during the actual movement of the rod 56 in tripping the clutch.

It is desirable in machines of the types contemplated by the present invention to impart the same total pressure to every work piece, this pressure being measured by the shortening of the spring 40 as the toggles 18, 20 are straightened. It is obvious that if the work pieces vary in thickness the shaft 12 will be raised varying amounts by the. initial movement of the treadle 52 and that therefore if the toggles 18, 20 are connected directly to the shaft 12 and to the plunger 36 the shortening movement of the spring 40 will vary in different cases with different work pieces. In other words, with a construction such as suggested the total distance from the ack 14 to the top of the plunger 36 when the toggles are straightened is always the same and the thicker the work piece the more the compression of the spring 40 when the toggle is straightened. It has therefore been advisable in presses of this type to provide a so-called measuring mechanism which in effect varies the effective length of the pressure imparting mechanism so that the fundamental pressure imparting element will exert the same total pressure upon any work piece. Accordingly, the illustrated machine is provided with an adjustable element in the chain of pressure imparting elements. to alter its effective length. As herein disclosed, this element is inserted between the pin 28 and the top of the plunger 36. The pin 30 carried at the lower end of the toggle link 20 is mounted for vertical sliding movement in the slots 32 in the top of the plunger 36. As the work support 14 and with it the toggle links 18, 20 are raised during the earlier part of the treadle movement the pin 30 moves upwardly in the slots 32. The measuring device or adjustable element above spoken of comprises a wedge 68 mounted for forward and rearward sliding movement between the pin 30 and a surface formed on the top of the plunger 36. The wedge 68 is connected at its rear end to a link 70 to which is fastened one end of a tension spring 72, the front end of the spring being secured to a pin in the top ofthe'plung er 36, so that as the toggle member 20 is raised by the initial movement ofthe treadle the wedge 68 is pulled forwardly by the spring 72, thus contactin at all times with the pin 28 and the upper end of the plunger 36. Thus, irrespective of the thickness of the work, the same toggle action will produce the same amount of compression of the spring40.

Means is provided for withc rawing the wedge 68 as the machine is operated to lower the work support after the compression of a piece of work and for latching the wedge 68 in its with-drawn position while the machine is at rest with the work support 14 lowered. For this purpose a circular cam groove 74 is provided in a member attached to the shaft 48 having a shouldered block 76 mounted fixedly in it -:and arranged partially to lock the cam groove 74 at that point. The rear end of the link 70 carries a semi-cylindrical pin 78 which can slide over the top of the block 76 when the righthand end of the link 7 0 is raised but will hook over the righthand end of the block 76 when the link 70 falls. The initial movement of the treadle raises the link 80 and lug 82 which contacts with the endof the link 7 O to raise the pin from the end ofthe block 76, thus permitting the spring 72 to pull the link forward and drive in the wedge 68 between the pin 28 and the top of the plunger 36 as the pin rises to bring the work piece against the member 16. After the cam groove 7 4 has revolved about 180 the right-hand end of the block 76 will catch the pin 78 and pull the Wedge to the right prior to which time the toggle 18, 20 will again have been bent.

The *ed 'e 68 thus forms an automatically adjustable measuring member or abutment the ultimate forward position of which is determine d by the extent to which the work support 14 is raised by the rod 56 and constitutes in effect a measuring device which compensates for the Varying thicknesses in work inserted between the members 14 and 16, thus enabling th initial movement of mechanical pressure to take place with the toggle links 18, 20 and the spring 40 in the same relative positions and thus compressing the spring 40 to the same amount in all cases, thereby -applying a uniform pressure to all work pieces. 7

It has been found under practical working conditions, such as proper lubrication of the wedge and its engaging surfaces and the unavoidable jars of machine operation, that the maximum angle permissible between the upper and lower surfaces of a simple wedge, that is, a wedge with plane wedging surfaces, is about 7 and that if this angle is made any steeper the wedge willslip and will be forced ont wl-ren the pressure is applied. The length of such a wedge which would be requisite to compensate for such variations in work thickness as are aften met with and the length of its path of movement are so great as to render such a mechanism impractical under many conditions. Accordingly, for increasing the friction between the wedge and the surfaces with which it engages so that a wedge of considerably steeper angle can be successfully used, I form a bevel on one or both of the relatively inclined'wedging surfaces 101, 102 of the wedge, as shown particularly in Figs. 4, 5: and 6, forming correspondingly shaped grooves in the pin 80 and in the topof the plunger 36. These bevels run from the wedging faces 100, 102, respectively, to the side faces 104, 106 of the wedge. The groove in the plunger 36 is .clearly shown in Fig. 3 at 82 and the groove in the pin 30 is of similar formation (see Fig. 2). In the disclosed machine the converging angle between the beveled surfaces at the top of the wedge is 20 and between the surfaces at the bottom of the wedge is 30. The angle between the top and bottom surfaces of the wedge is 25.

In order to consider the theoretical principles involved in this construction reference is made to Figs. 7 and 8. Fig. 7 shows a cross-sectional view of the pin 80 and the Wedge 68, the section being taken perpendicular to the upper edge of the wedge 68 and to the bottom of the correspondingly shaped slot groove in the pin 30. The reaction aetween the pin and the wedge perpendicular to its edge is denoted by F. The half angle of the bevel is denoted by a. One-half of the force F is carried on each beveled face at the top of the wedge and is balanced by a force G perpendicular to the face of the bevel. Therefore, the force pressing the beveled face of the wedge against the inclined face of the slot in the pin 30 is 2 sin 0:

and if a is made sufficiently small G can be made as large as desired. The same conditions obtain at the beveled surface at the other side of the wedge so that the total pressure exerted perpendicularly between the beveled surfaces of the wedge and the sloping sides of the slot in the pin is equal to sin a The friction or force which opposes any force tending to produce sliding of the Wedge upon the pin is equal to the product of the forces pressing them together along their sliding surfaces multiplied by the coefficient of friction between such surfaces formed in such materials. As will be shown below, the safe maxim-um assumable coefficient of friction between machine surfaces of this kind is abont006 and therefore the force opposing sliding between the wedge and the substitute in (1) friction between the wedge and the pin in the who I sma and the theoretical discussion of the action of the mechanism disclosed can be carried through by assuming a simple wedge working on flat surfaces on the pin and 011 the top of the plunger 36.

Fig. 8 illustrates diagrammatically a cross section of the pin 30 and of the wedge 68.

The pin 30 is acted on by five forces: A, verti ally downward; B, the horizontal reaction bet-ween the pin and the side of the slot Bf, the friction between the pin and the side of the slot, acting vertically upward, being the coeliicient of friction between the slot face and the pin; (l, normal to the lower inclined surface of the pin; and Cf, the friction between the pin and wedge, actin upwardly along the inclined surface, f being the effective coeilieient of friction between the pin and the wedge.

The wedge is acted on by live forces: 0, normal to the upper, inclined surface; Cf,

tan0

Eliminate B from (1) and (2) from (2) we get A=O (eosB-l-f sin 0+ sin6-fi" cos 0) (1j cos0+ (f+f) sin0 Substitute (4) and in for the limiting condition, P is zero. Hence sinfi (lff) =eos0 (f' +f) The effective coel'licients of friction on the 'l n beveled wedge races are, therefore, with the 10 and bevels assumed:

And the limiting value of 6 is given by (7) It is thus possible. with the construction shown to use safely a wedge having an angle of over between its top and bottom surfaces. lt is interesting to notice that for the limiting condition as set fort-h in equation (7) the angle of the wedge is equal to the sum of the angles whose tangents are f, 7', that is, the two effective coeiiicients of friction at the top and bottom of the wedge.

The angles of bevel at the top and bottom of the wedge can be conveniently chosen to meet the conditions of any particular situation. It might be stated that the reason that different angles of bevel were chosen for the top and bottom of the wedge in the instant case was to facilitate somewhat the withdrawal of the wedge on release of pressure by diminishing the frictional force between the bottom of the wedge 68 and the top of the plunger 36, it having been found that this could be done with perfect safety.

As above described, the pressure supporting element or wedge 68 is a modified form of simple wedge. A simple wedge is a body mounted in part by two planes at an angle with each other, thus forming a dihedral angle, called the wedging angle, or angle of the wedge. These surfaces correspond to the surfaces 100, 102 in the illustrated wedge, and the wedging angle of the simple wedge corresponds to the dihedral angle between them, the vertex of which, called the edge of the Wedge, is a line perpendicular to the plane of Fig. 4E, and passing through the point 108 at the vertex of the angle of 25. The side faces of the simple wedge are two planes generally perpendicular to the edge of the wedge, cutting off a desired portion of the dihedral angle. These side faces in the wedge shown in Fig. 4 are the surfaces 104, 106.

In the illustrated wedge of the present invention the simple wedging faces 100, 102 are each beveled as shown in Figs. l. 5 and 6, at 110, 112, the bevels running from the wedging faces to the side faces. Thus the effective wedgin g faces are compound, comprising these bevels, instead of simply plane as in the simple wedge. These compound surfaces, as far as their wedging action is concerned, operate like a simple wedge of the illustrated wedging angle of 25. Their holding power under pressure, however, is not determined by this wedging angle, as it is in the case of the simple wedge, but by the angles between the beveled elements (20 and 36 in the illustrated wedge). As already shown, the holding power can be made as great as desired for any wedging angle. This enhanced holding power is due to the fact that the beveled surfaces of the wedge are placed at a small and disadvantageous angle to the line of pressure resisted by the wedge as a whole. Thus that component of the pressure exerted by the beveled surface which is efiective in balancing the external force transmitted to the wedge is a small part of the pressure exerted by (and on) the beveled surface. This pressure is therefore made very large, and the friction resulting from it is correspondingly large.

While the invention has been disclosed as embodied in a pressing machine, it is of considerably wider application, as for example, in machines for clamping work upon which some operation is to be performed and the appended claims are not be understood as limited to the particularly embodiment of the invention selected for disclosure.

Having described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In a pressure-supporting device, two pressure-supporting members, and a wedge arranged to be inserted between them to hold them at varying d1stances, said wedge havmg one of its faces beveled along the edges, and the corresponding said pressure member being provided with surfaces correspondingly formed to engage the beveled face of the wedge, the angle of the bevel being such as to set the beveled wedging face at an angle of less than 45 to the direction of the pressure exerted by the pressure supporting memmembers having their wedge-engaging facescomplementarily shaped, respectively, whereby the friction between the wedge and the sustaining members may be increased.

8. In a pressure-supporting device, two pressure-supporting members, and a wedge arranged to be inserted between them to hold them at a predetermined relative distance, said wedge having one of its operative faces beveled along an edge, and the corresponding said pressure member being correspondingly formed to engage the beveled surface of the wedge, the an de of the wedge being greater than ten degrees.

4. A pressure supporting wedge having a wedging surface making an angle of more than 135 with a side face of the wedge whereby the effective coefficient of friction between the wedge and a complementarily formed contact member may be substantially increased.

5. A pressure supporting wedge having a compound wedging face comprising converging surfaces substantially oblique to the edge of the wedge, the angle of obliquity being such as to cause that component of the force exerted by a said wedging face which is effective in balancin the external pressure transmitted to the wedge to be relatively small as compared with the said force.

6. A pressure supporting wedge having a compound wedging face comprising two planes oblique to each other and to the side face of the wedge, the angle between the said planes themselves being less than 90, whereby the efiective coefficient of friction between the wedge and a complementarily formed contact member may be substantially increased.

7. A pressure supporting wedge having two wedging surfaces, one of which comprises two planes at an acute angle with each other, the line of intersection of the two planes intersecting the other wedging surface, thus forming the wedging angle of the wedge.

8. A pressure supporting wedge having two wedging surfaces each comprising a pair of planes at an acute angle with each other, the lilies 0t intersect-ion of the two pairs of planes intersecting at an acute angle.

In testimony whereof I have signed my name to this specification.

THOMAS H. SEELY. 

